**ULTIMATE EDITION** This document includes all IT Theory content from grade 10 to grade 12. It contains all the necessary information in a colourful, table format. Diagrams of complex topics have been included. All information has been typed for improved legibility. These notes have been used by h...
LU1 Data Representation and Storage
1. Decimal, Binary and Hexadecimal Number Systems
2. Number of Combinations for Number of Bits
3. Data Storage
4. Digital Representation of Numbers
5. Digital Character Representation
6. Storing Screen Data
LU2 Overview of a Computer
1. Hardware and Software
2. Advantages and Disadvantages of Using Computers
3. Data and Information
4. Computer System Types
5. Operating Systems
6. Application Software
7. Data Transfer and Synchronisation Between Devices
LU4 System Software
1. Parts of System Software
2. Software Distribution and Licensing Models
3. Structuring Data in Secondary Storage
4. System Management
5. Security Features
LU5 Computer Networks
1. Networks, Nodes and Communication Media
2. Bounded Media
3. Unbounded Media
4. Network Classification
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5. The Home Network and Network Access Control
(NAC)
6. Advantages and Disadvantages of Computer
Networks
LU7 Internet and WWW
1. The Internet and its services
2. IP Addresses
3. What is Needed to Connect to the Internet
4. The World Wide Web (WWW)
5. Searching the Web
6. User Interface Design
LU8 Social and Ethical Issues
1. Economic Reasons for Using Computers
2. Digital Divide
3. Ergonomics
4. Green Computing
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LU1 - Data Representation and
Storage
1. Decimal, Binary and Hexadecimal Number Systems
Binary Decimal Decimal
● Continuously divide by 2 ● Order the binary number in ● Order the hex number in
● Write down the remainder columns with increasing columns with increasing
● Repeat until the quotient is 0 powers of 2 powers of 16
● Read the remainders from ● Going from right to left, ● Going from right to left,
bottom to top starting at 0 starting at 0
● Multiply the bit by the ● Multiply the integer value
Base 140 Remainder
power of 2 in its column by the power of 16 in its
2 70 0 column
2 35 0 27 26 25 24 23 22 21 20 161 160
2 17 1 1 0 0 0 1 1 0 0
8 C
2 8 1
2 x 1 = 128 +
7
2 x0=0 6
8 x 161 12 x 160
2 4 0 25 x 0 = 0 + 24 x 0 = 0
2 x1=8
3
+ 22 x 1 = 4
128 12
2 2 0
2 x0=0
1
+ 20 x 0 = 0
1000 11002 = 14010
2 1 0 128 + 12 = 140
2 0 1
8C16 = 14010
14010 = 1000 11002
Hexadecimal Hexadecimal Binary
● Continuously divide by 16 ● Number of bits must be a ● First convert to decimal as
● Write down the remainder multiple of 4 shown above
● Repeat until the quotient is 0 ● Leading zeros must be ● Then use the decimal
● Read the remainders from added method to convert to
bottom to top ● Split the binary number into binary
groups of 4 bits
0 1 2 3 4 5 6 7 8 9
● Multiply each bit by the
0 1 2 3 4 5 6 7 8 9 multiple of 2
● Match the Hex value
10 11 12 13 14
1 0 0 0 1 1 0 0
A B C D E
x x x x x x x x
23 22 21 20 23 22 21 20
8C16 = 1000 11002
Base 140 Remainder
8 0 0 0 8 4 0 0
16 8 12
8=8 12 = c
16 0 8
161 162
8=8 12 = C 8=8
8 C
14010 = 8C16
1000 11002 = 8C16
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2. Number of Combinations for Number of Bits
Word Size ● The number of bits that the processor of a computer can work with at
one time.
● Bits are grouped together into units called words (32 or 64 bits)
E.g. Word size of 4 bits
● Number of combinations is calculated as 2n where n is the number of
bits
● (24) = 16 combinations
3. Data Storage
Data Storage ● The size of memory capacity such as RAM and HDDs is measured in
multiples of bytes.
● b = bits B = bytes
● 8 bits = 1 byte 1024 bytes = 210 bytes = 1 KB
4. Digital Representation of Numbers
Digital Representation Integers are positive whole numbers, negative whole numbers or 0.
An integer consists of two parts:
● Sign: (+ or -)
● Value: 56
Integers without a sign can only be positive and are known as unsigned.
Integers with a sign are known as signed.
Unsigned Integers ● Uses all of the allocated bits to represent the value of the number
● Can only be a positive whole number
● Largest unsigned integer: 2n - 1
● Smallest unsigned integer = 0
Signed Integers ● The first bit is used to represent the sign of the number (0 = +; 1 = -)
● Can be any whole number
● Largest unsigned integer: 2n-1 - 1
● Smallest unsigned integer = -2n-1
Summary of Formulae
Integer in limited Smallest Largest Number
bits Number
n unsigned bits 0 2n - 1
n signed bits - 2n-1 2n-1 - 1
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Primitive Data
Name Description Size Range
char Character or small 1 byte signed: -128 to 127
integer unsigned: 0 to 255
short Short integer 2 signed: -32768 to 32767
int bytes unsigned: 0 to 65535
(short)
int Integer 4 signed: -2147483648 to
bytes 2147483647
unsigned: 0 to 4294967295
long Long integer 4 signed: -2147483648 to
int bytes 2147483647
(long) unsigned: 0 to 4294967295
bool Boolean value. It can 1 byte true or false
take one of 2 values:
true or false
float Floating point number 4 +/- 3.4e +/- 38 (~7 digits)
(real) bytes
double Double precision 8 +/- 1.7e +/- 308 (~15 digits)
floating point number bytes
(real)
long Long double precision 8 +/- 1.7e +/- 308 (~15 digits)
double floating point number bytes
(real)
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5. Digital Character Representation
American Standard Code ● First widely used character set
for Information ● Each character was represented in 8 bits; total combinations (28 = 256)
Interchange Problems:
(ASCII) ● Certain languages required more codes than the encodings could
provide
● Encodings were not consistent - some values overlapped
● Computers could not transfer encodings - lead to corrupt data
Unicode and Unicode
Transformation Format Unicode ● Unique number for every character - universal
● Can be interpreted across different computers
(UTF-8)
● No chance of data corruption due to
inconsistent encoding
UTF-8 ● Each character is represented by at least 8 bits
per character (1 byte)
● Characters can use up to 32 bits (4 bytes)
Inserting Symbols Combinations of ALT, CMD and OPTION all
and Characters correspond to various symbols and characters
6. Storing Screen Data
Screen Data and ● The computer needs to display the correct and readable data on the
Refreshing screen in real-time
● Each change is updated immediately.
● This could be a result of the user switching between application
windows or entering in data.
● The computer uses a process of refreshing - it redraws the screen at a
certain rate. This rate is measured in hertz (Hz) which is the number of
updates by second
Representing Colour ● Pixels are tiny dots on the screen
● Each pixel has its own colour definition
● Colour can be defined either in RGB or some other colour definition
● RGB (Red Green Blue) is a system of producing any colour light by
adding varying intensities of red, green and blue light
● Each colour is represented by a byte.
● Recall that a byte has 256 combinations numbering from 0 to 255.
Red Green Blue
bytes 128 0 255
bits (binary) 10000000 00000000 11111111
Screen Resolution Number of horizontal and vertical pixels that can be displayed on the screen
Total bytes of RAM used = (Screen resolution) x (pixel byte value)
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LU2 - Overview of a Computer
1. Hardware and Software
Hardware and Software They interact together to ensure that the computer can successfully:
● Receive input data
● Process the data
● Store the data
● Output the information
● Neither could exist on their own
Hardware The collection of physical components attached to
the computer system
Software The collection of non-physical parts of the system
(OS, apps and data)
General Processing Cycle ● The CPU is fed instructions that are stored in RAM
● RAM receives data from input devices
● Sends data to an output device
CPU can only execute instructions that are in RAM
Connectivity and an ICT ● ICT - Information and Communication Technology
System ● With internet, computers ‘talk’ to each other and exchange data
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